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/*******************************************************************
 * © 2024 SAP SE or an SAP affiliate company. All rights reserved. *
 *******************************************************************/
package com.sap.cds.ql.cqn;

import java.util.List;

/**
 * A case expression, which represents IF - THEN - ELSE logic. The result value
 * is determined by evaluating a list of {@link Case cases}. If a
 * {@link Case#condition()} of a case evaluates to TRUE the {@link Case#value()
 * result value} of the case is returned. If no condition of any case evaluates
 * to TRUE the {@link #defaultValue() default value} is returned.
 */
public interface CqnCaseExpression extends CqnExpression {
	/**
	 * The {@link Case cases}, which are evaluated.
	 * @return the cases
	 */
	List cases();

	/**
	 * A case, which relates a condition to a result value.
	 */
	interface Case {
		/**
		 * The condition 
		 * @return the condition
		 */
		CqnPredicate condition();

		/**
		 * The result value
		 * @return the result value
		 */
		CqnValue value();
	}

	/**
	 * The default value, which is returned if no condition of any case matches
	 * @return the default value
	 */
	CqnValue defaultValue();

	@Override
	default boolean isCaseExpression() {
		return true;
	}

	@Override
	default CqnCaseExpression asCaseExpression() {
		return this;
	}

	@Override
	default void accept(CqnVisitor visitor) {
		for (Case c : cases()) {
			c.condition().accept(visitor);
			c.value().accept(visitor);
		}

		defaultValue().accept(visitor);

		visitor.visit(this);
	}

}